Now on AliExpress (use the app!!!) a NEO Coolcam NAS-DS01Z Smart Home Z-Wave Plus Door Window Sensor for only €15,61 (If you order without the AliExpress App they are €16,30)
I have a couple of them in my setup and they work like a charm with Domoticz.

These are really nice.
Note that you have to add them to your z-wave network through Domoticz. If you try to add them directly with a z-stick, the device is not detected properly. That took me quite some time to figure out